If you own a laptop, chances are that you often wondered what was that little cylinder at the end of your charger wire.
 |
| Cute Little Cylinder at the End of My Laptop Charger |
As it is worthwhile to know what it is as it has interesting physics behind it. Perhaps or Surely you are all acquainted with what an inductor is. But for a general reader, I would like to clarify it a bit more. An inductor is a coil of wire that has the property of building up a magnetic field associated with it.
 |
| An Inductor |
But there is a rule called Lenz law that tells you that there is no free lunch in mumbo-jumbo terms. This rule is given in the usual text book jargon below :
So, as the inductor is reluctant to change the magnetic field associated with it, it offers a resistance to the flow of current in proportion to the rapidity with which the current changes. High frequency currents changes their polarity more frequently than their low frequency fellow currents.In essence an inductor is not well with the high frequency currents and block them then and there to a greater extent than low frequency currents. Not only coils of metal, but a ceramic material called Ferrite (which is basically rust mixed with certain other metals) surrounding a single wire can act as a sort of inductor. If AC power is supplied to a sensitive electronic device which our laptop certainly is, it is wise to surround the wire near the end of charger wire by Ferrite cylindrical shell for the following two reasons:
- AC power lines come with spikes, i.e., sudden variation in supply voltages which passed through the SMPS (oh ! that black brick which we call charger) affect the performance of our Laptop.
- The long charger wire acts like an antenna, and due to EMI (Electro Magnetic Interference) may feed all sort of unwanted signals into our laptops motherboard circuitry.
 |
| Charger Wire or Antenna ? |
So, to avoid these interferences and improve the performance charger manufacturers add a a small cylindrical shell of Ferrite ceramic material which is called a "Ferrite Bead".This Ferrite Bead effectively isolates the laptop from unwanted high frequency current noises, but let the DC component of current charging your laptop to pass through.
 |
| Ferrite Bead with Plastic Cover Removed |
Credits: By Omegatron - Taken by User:Omegatron using a Canon Powershot SD110, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3842054
So this tiny little cylindrical shell at our charger wire let to us to contemplate a bit of curious physics behind it. I am positive that this post interested you and you are eager to know more facts how physics play a central role in every piece of technology. I'm also eager like you and whenever I stumble on a good one I shall let you know that. If you have observed something curious please bring it to my attention through the comments.
